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SubjectRe: [PATCH v6 1/2] spi: add support for DLN-2 USB-SPI adapter
On Wed, Nov 26, 2014 at 12:09:09PM +0200, Laurentiu Palcu wrote:

> +static int dln2_spi_transfer_one_message(struct spi_master *master,
> + struct spi_message *msg)
> +{
> + struct dln2_spi *dln2 = spi_master_get_devdata(master);
> + struct spi_device *spi = msg->spi;
> + struct spi_transfer *xfer;
> + int status;
> +
> + list_for_each_entry(xfer, &msg->transfers, transfer_list) {
> + u8 attr = 0;
> +
> + status = dln2_spi_transfer_setup(dln2, xfer->speed_hz,
> + xfer->bits_per_word,
> + spi->mode);
> + if (status < 0) {
> + dev_err(&dln2->pdev->dev, "Cannot setup transfer\n");
> + break;
> + }
> +
> + if (!xfer->cs_change &&
> + !list_is_last(&xfer->transfer_list, &msg->transfers))
> + attr = xfer->cs_change ? 0 : DLN2_SPI_ATTR_LEAVE_SS_LOW;
> +
> + status = dln2_spi_rdwr(dln2, xfer->tx_buf, xfer->rx_buf,
> + xfer->len, attr);

We recently added a spi_transfer_is_last() operation which should allow
you to move this to using transfer_one() which is a bit nicer.

> + /* enable SPI module, we're good to go */
> + ret = dln2_spi_enable(dln2, true);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "Failed to enable SPI module\n");
> + goto exit_free_master;
> + }

It would be nice to have runtime PM operations which keep the device
disabled when idle, presumably that'd save a bit of power and it's
generally better practice.
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